This doesn't answer your question but...
Seems to me that shopping cart decisions are really better made when you know exactly what it is you want them to accomplish.
Once you know what you really need it to do, there are so many options to choose from, and many are free and opensource and rival the features of proprietary systems.
From simple add to cart buttons and payment processing of Mals, to full blown carts that allow for special group pricing (wholesale and retail, or member and non-member), affiliate plugins and upsale capabilities, product reviews and ratings, custom payment options, etc of virtuemart, oscommerce or magento, or a paid solution, it's always in my mind, best to match your needs with the cart rather than the other way around. Makes it easier to not have to pay for features you don't necessarily need.
Just my .02....
1Shopping Cart vs Premium Web Cart
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